Hyundai Motor Co has recalled 240,000 Elantra sedans because the computer that operates the air bag system could confuse a child seat for an adult in the front passenger seat.

Hyundai Motor Co said on Thursday it would recall 240,000 Elantra sedans in the United States because the computer that operates the air bag system could confuse a child seat for an adult in the front passenger seat.

The recall involves vehicles from the 2004-2005 model years. The Elantra is the South Korean-based automaker's most popular-selling vehicle in the United States.

Hyundai said an evaluation conducted by the National Highway Traffic Safety Administration found that a child seat in the front passenger seat could be misclassified by the air bag sensor system as an adult passenger.

The circumstances are limited,Hyundai said it could only happen if a child seat was installed after an adult had been in the passenger seat and then the ignition was turned off. Under that scenario, when the vehicle was turned back on, the system's memory would misinterpret the child seat as an adult passenger. It could lead to the deployment of the front air bag and side-impact air bag in a crash, the company said. Normally, those air bags would not deploy if the system properly identified a child restraint seat because the impact of the bags could injure a child. "At the end of the day it's to ensure the safety of someone who rides in the child seat," said Hyundai spokesman Miles Johnson. He noted that the federal government recommends that all children under 13 sit in the rear seats.

There have been no crashes or injuries connected to the issue, Hyundai said.

Owners are expected to be notified by mail in October. Dealers will fix the problem by reprogramming the computer system. The Elantra starts at $13,299, according to the automaker's Web site. Hyundai issued a separate recall in August of about 36,000 2006 Sonata sedans because of problems with the driver's seat belt getting caught up with a knob used to recline the front seat.